1. Field of the Invention
The invention is concerned with an exhaust gas recirculating system for turbocharged engines. More particularly the invention is concerned with a unique improvement in a turbocharged engine system which makes use of a split or divided exhaust manifold whereby only a portion of the pistons of an engine driven within the respective cylinders thereof will recirculate exhaust gas into the inlet manifold.
2. Prior Art
In normal turbocharged engines the inlet manifold pressure exceeds the exhaust manifold pressure at high loads. This imposes a pumping requirement if exhaust recirculation is to be accomplished. With some types of pumps the recirculated exhaust cannot easily be metered to meet the requirements of the engine. Typical exhaust recirculation systems of the prior art are shown for example, in U.S. Pat. Nos. 3,713,428; 3,738,342; and 3,587,541. Copending and commonly assigned U.S. Patent Application Ser. No. 583,230 filed June 2, 1975, now U.S. Pat. No. 4,020,809 discloses yet another exhaust gas recirculation system for a diesel engine, particularly one in which nitrogen oxide emission is reduced.
It is clear that none of these references are in any way concerned with an exhaust gas recirculation system for a turbocharged engine wherein the system will provide pumping and metering functions for exhaust recirculation on a turbocharged engine and exhaust recirculation means piping the exhaust from only a portion of the pistons of the engine into the inlet manifold in order to reduce the production of oxides of nitrogen. Some of the advantages of such a system are that it eliminates the need for an external pump, it does not cause back pressure on more cylinders than are necessary, it can be controlled to any exhaust recirculation schedule that is required and transient performance need not be deteriorated. All of these advantages are attained by the novel improved exhaust recirculation system of the present invention in a manner which is explained in the following.